Drying and chilling chamber



Nov. 30, 1943. w. s. BOWEN DRYING AND CHILLING CHAMBER Filed Dec. 21, 1939 INVENTOR WEI/1am dga nrer Bauer/t ,a fi r mqzvs Patented Nov. 30, 1943 UNITED STATES PATENT OFFICE DRYING AND CHILLING CHABIBER William Spencer Bowen, Westfield, N. J.

Application December 21, 1939, Serial No. 310,312

4 Claims.

This invention relates t the spray processing of fluids and semi-fluid substances, and has particular reference to an improved method of desiccating or chilling liquids and plastic materials, and apparatus for accomplishing the same.

- Desiccation of the solid constituents of fluids and the hardening of semi-fluid substances such as soaps, resinous plastics and the like, may be accomplished by spraying the material in finely divided form into a counter-flow of a gaseous desiccating or chilling medium. With a relatively unconfined flow of gaseous treating medium, proper control of the desiccating or hardening action to obtain a uniform product is diflicult of achievement, due to variation in the particle size of the sprayed material with corresponding fluctuation in moisture content, and the tendency of the larger particles to prematurely discharge and the flow of treating medium due to their greater weight before proper modification of their physical properties is accomplished. Moreover, chilling or drying of the particles becomes increasingly diflicult as the percentage of free moisture in the particles decreases.

Though the particles are subjected to substantially identical treatment by the gaseous treating medium, there is frequently undesirable retention of free moisture by the particles due in part to the formation of a relatively nonporous casing on the particle surface, which offers increasing resistance to withdrawal or freezing of the moisture content of the particles, as the process is carried to completion.

Accordingly, it is an object of the present invention to provide a method of treating substances in particle form wherein the physical properties of the treated particles are rendered substantially uniform, regardless of variations in particle size.

A further object is to provide a method of desiccating or chilling fluids which provides a maximum of desiccating or chilling action at that phase in the process wherein modification of the physical properties of the particles is most diflicult.

of the fluid particles from the flow until their physical properties are altered to a desired degree.

A further object is to provide a method of spray-drying or chilling semi-fluids such as soaps and glues wherein deformation of the particle contour by objectionable contacts during treatment in the drying chamber is minimized.

Still a further object of the present invention is to provide an improved apparatus for carrying out the method of the present invention.

Further objects and advantages will be apparent from the following description of the invention and the drawing, wherein:

Figure 1 is atop view of apparatus constructed in accordance with the present invention with a portion in section to indicate the interior formation of the drying or chilling' chamber;

Figure 2' is a view in vertical section taken along the line 22 of Figure 1 and in the direction of the arrows;

Figure 3 is a view similar to Figure 2, showing a further embodiment of the present invention, wherein the gaseous treating medium is introduced circumferentially of the drying chamber; and

Figure 4 is a view in vertical section of a modifled form of drying chamber constructed in accordance with the present invention.

Referring to Figures 1 and 2 of the drawing, the numeral I0 indicates the spray-processing chamber shown as a vertically positioned cylindrical tower having a bottom portion ll converging downwardly to form a cone leading to a particle discharge outlet l2, which discharges the treated material onto a suitable conveyor l3. The treating medium, which for purposes of desiccation of the particles would be a heated gaseous medium such as air, is introduced into the spray-processing chamber through a jet or nozzle 14 positioned axially of the cone H and supplied with drying medium through a conduit IS. The material to be treated is introduced into the cylindrical chamber ID by means of a suitable spray device l6 supplied with material through a conduit ll. The spray device I6 is supported axially of the chamber 10 by an outlet manifold l8 which encloses the open end of the chamber ID to form an annular exhaust duct I9 about the periphery of the said chamber for the removal of spent, moisture saturated drying medium therefrom, the manifold discharging through a conduit 20.

The material to be treated is sprayed through the head I 6 to form a diverging spray of material in the chamber l0, which falls by gravity into a rising counter-flow of drying medium from the nozzle ll.

The walls of the cone ll flare outwardly from a point above the particle outlet i2 at an angle not exceeding 20- and preferably about 8, the flare being gradual to permit an orderly, nonturbulent distribution of the drying medium across the diameter of the cone, preventing the formation of undesirable eddy currents or dead air spaces in the cone area. The nozzle l4 preferably is formed to discharge into the cone II, a flow of drying medium having a relatively high axial velocity. The flow expands radially in its upward path to follow the contour of the cone,

providing a flow of comparatively lower velocity about the inner circumference of the cone Ii. The initial mean velocity of the drying medium upon discharge from the nozzle l4 preferablyis controlled to provide a strong flow at the area of the nozzle II which gradually decreases in velocity as it rises and expands across the cone ii. For example, introduction of the drying medium into the cone l I at an initial velocity of 6000 feet per minute will obtain a velocity of drying medium in the chamber l approximating 100 feet'per minute, the latter figure, of course, being determined to some extent by the length and flare of the cone ll. Thus, the flow of drying medium provides a gentle preliminary desiccating action in'the cylindrical chamber i0,

permitting the relatively moist particles to fall uniformly through the drying medium with a minimum of turbulence.

The chamber I 0 is formed cylindrically for such. a length that the moist relatively plastic particles will cease to be taclw before discharge into the cone Ii, thus eliminating undesirable adhesion and packing of the particles on the walls of the apparatus, particularly upon the converging walls of the cone H. The length of the cylindrical chamber ill will vary necessarilywith the physical properties of the material under treatment. For example, desiccation of thin liquids requires a longer preliminary drying treatment to remove the adhesiveness of the material, than do semi-fluids such as syrups, or plastics. In'such case,- the length of the cylindrical chamber i0 should be extended considerably. With the chilling or freezing of materials, it has been found that some materials chill more readily than others, for instance, particles of soap chill more rapidly than glue. The desirable length of the chamber ID will also vary with the size of the particles under treatment. smaller particles having relatively less surface area and weight and thus encountering less frictional resistance to their gravitational fall.

A preliminary hardening of the particles being accomplished in the'chamber l0, the particles penetrate the counter-flow of drying medium in the cone l l, the velocity of the drying medium gradually increasing as the particles in their gravitational fall approach the particle outlet l2. It will be observed that the intensity of the drying action in the cone ll increases as the moisture content 'of the falling particles ap-' proaches theminimum at which a complete transition of the particles to solid, dry form is most diflicult of accomplishment.

As pointed out heretofore, upon introduction of the drying medium axially of the cone II, the velocity of the drying medium will be greatest at the central area of .the cone, the velocity thereof about the inner circumference being appreciably reduced due to the formation of the nozzle l4, and the contact friction with the walls of the cone ii. During the gravitational fall of the particles, at some point midway of the cone II, the kinetic energy of the falling particles and the counter-flow of drying medium will balance, the point of balance varying considerably with the physical properties, weight, density and surface area of the material under treatment. Upon attainment of this point of balance, the particles will tend by gravity to seek that portion of the gaseous flow offering the minimum of resistance thereto, working to apoint adiacent the walls of the cone H and then downwardly to the particle discharge outlet l2. As is shown in Figure 2, the desiccated or hardened particles collect in the outlet l2 above the conveyor i3, effectively sealing the bottom of the cone ii to prevent drawing of air into the cone by the draft induced by the nozzle it.

Because of their greater weight. and surface :area, the larger ,particlesfwill receive a more extended treatment than the smaller particles, the kinetic energy of the larger particles being relatively greater to thereby extend the degree of penetration into the cone ll before the kinetic energy of the particles and drying medium balance. As the larger particles more tenaciously occlude their moisture content, this extended phase of treatment for the larger particles lends to greater uniformity of product, minimizing the effects of variation in particle size. Further, as the flow of drying mediunidiverges across the entire transverse area of the cone H to completely eliminate the presence of dead air zones therein, the fortuitous premature discharge of particles from the drying zone is eliminated.

In Figure 3 of thedrawings, there is shown a modification of the invention wherein the drying ence of the cone H. In this instance, the lowest velocity of'the counter-flow is found in the area extending axially through the cone Ii, and the particles under treatment will work ultimately to the axial discharge outlet 24, in the manner heretofore described.

In Figure 4, the apparatus of the invention is shown in a form modified toprovide a chamber 25 having a number of frusto-conical wall segments 20 which are flared in increasing degrees of angularity from theaxis of the conical chambar. This embodiment of the invention is particularly adapted for use when a prolonged preliminary drying treatment of the falling particles in the cylindrical chamber 10 is necessitated by the physical properties of the material under treatment. The angular structure of the walls of the chamber 25 may be varied within a wide range to provide a more accurately controlled velocity characteristic of the drying medium counter-flow, affording a series of clearly defined phases of mean velocity of the drying medium in the chamber 25. The drying medium may be introduced axially of the chamber25 by the nozzle M, or annularly of the chamber 25 in the manner shown in Figure 3.

While the invention has been-described as applied to the spray-drying of fluids and desiccation of semi-fluid materials, the apparatus and method of the invention are adapted readily to the chilling or freezing of such materials as soaps, soap powders, glue, syrup, resinous plastics and the like. Where the process is one of desiccation, it is essential only that the drying medium be capable of moisture absorption, the invention not being limited to the use of preheated gaseous drying mediums. With the chilling or freezing of materials, it is desirable in many instances that the moisture content of the sprayed particles be fixed therein with minimum loss of moisture by evaporation. Accordingly, the freezing medium should be saturated with moisture prior to refrigeration of the particles.

Due to elimination of the formation of uncontrolled eddy currents in the flow of treating medium through cone i I and chamber In, undesirable deformation of the falling particles by direct contact with the walls of the apparatus is avoided. The cushioning effect of the treating medium in the cone ll retards the fall .of the particles to the discharge outlet, eliminating the damage to particle form experienced with the drop forming shot tower types of drying or chilling apparatus presently in use.

The method of treating materials by spraying particles of the materials into a counterfiow of treating medium which constantly increases in velocity as the gravitational fall of the particles proceeds, brings the particles into the zone of maximum treatment at the time when complete modification of the physical properties of the particles is the most difiicult of accomplishment. The method of the invention further reduces the tendency of the particles to case harden under treatment, thereby improving the solubility characteristic of the product.

Due to the selective discharge of the modified particles from the zone of treatment in accordance with their weight, the product processed by the method of this invention exhibits uniformity of physical properties in a degree hitherto unattainable.

While the invention has been described with reference to a specific process and apparatus, the references theretoare made only by way of illustration and the invention is to be limited only as defined in the following claims.

I claim:

1. An apparatus for processing fluid and semifluid materials comprising a housing shaped to form at least in part a downwardly tapering conelike member, means for introducing the material to be treated in particle form into the upper portion of said housing, said housing having a bottom discharge outlet for the particles, gas inlet means adjacent to said discharge outlet, extending substantially axially of and within said housing and of lesser cross-sectional area than the adjacent portion of said housing, providing a passageway between said inlet means and said portion of said housing connecting said housing and said discharge outlet, and means for introducing a gaseous medium at high velocity through said gas inlet means into said housing to subject the particles of material to increasing resistance as they progress downwardly in their gravitational fall toward said discharge outlet.

2. An apparatus for processing fluid and semifluid materials comprising a housing shaped to provide an upper cylindrical chamber and a lower downwardly tapering cone-like chamber, the apex portion of said lower chamber. having a discharge outlet, means for introducing the material to be treated in particle form into the upper chamber for gravitation downwardly into the cone shaped chamber toward said discharge outlet, gas inlet means adjacent to said discharge outlet, disposed substantially centrally of and of lesser cross-sectional area than the adjacent portion of said lower chamber to provide a passage between said gas inlet and said adjacent portion connecting said lower chamber and said discharge outlet, and means for delivering a column .of a gaseous medium under pressure upwardly through said gas inlet means into the conical and cylindrical chambers counter to the gravitational movement of the particles to subject the material to increasing resistance as they progress downwardly in their gravitational fall toward said discharge outlet.

3. An apparatus for processing fluid and semifiuid materials comprising a housing shaped to form at least in part an elongated downwardly tapering cone-like chamber, means for introducing the material to be treated in particle form into the upper portion of said chamber, said housing having a bottom discharge outlet for the particles, an imperforate hood having a discharge outlet adjacent to its lower end covering the upper end of said housing in spaced relation to provide an annular exhaust outlet, a gas inlet nozzle in the lower portion of said chamber adjacent to said discharge outlet, said nozzle being of lesser cross-sectional area than said lower portion and disposed centrally thereof to provide a passage around said nozzle connecting said lower chamber and said discharge outlet, and means for delivering a column of a gaseous medium under pressure through said nozzle upwardly into said chamber counter to the gravitational movement of the particles to subject the particles of material to increasing resistance as they progress downwardly in their gravitational fall toward said discharge outlet.

4. An apparatus for processing fluid and semifluld material comprising a housing shaped to form at least in part an elongated downwardly tapering cone-like chamber having walls formed of a plurality of frusto-conical segments with each lower successive segment being of smaller average diameter than the next upper adjacent segment, means for introducing the material to be treated in particle form into the upper portion of said chamber, said housing having a. bottom discharge outlet for the particles, a nozzle adjacent said discharge outlet and spaced from the walls of said chamber to provide a substantially annular passage through which processed material can escape to said discharge outlet and means for delivering a gas at high velocity through said nozzle to subject the particles of material to increasing resistance as they progress downwardly in their gravitational fall toward said discharge outlet, said column of gaseous medium being restricted in area adjacent to said nozzle to permit processed material to escape downwardly through said passage.

WILLIAM SPENCER BOWEN.

cn'nnncmrfs OF c' RREcTIon. 4 I ..'Novemb'er 3 19 5- mm'n ;,35'5 752 uILLImsrmlvclsn mum Itie hereby certifiedthat error appears in the printed. epuuriuu n or the above numbered pqfzent rewiring cbrre'ctieii aifellb'we: Page 1, gm

cblmnn, 11m 1 for ".and' et't'er'diechlrge' read -'-rrom---; add that the said-Letters Patent should be read with this correction therein that the' same may'contorm to the ecan: or the eeee in the-Retort crude;

Signed and sealed thi e lsth day or Ja uary, A. 13.19%.

fienry veg-Arm n, (Seal) Actingcomniesioner pf Patente. 

